Simplified some of the GUID code.

This change applies some recommendations from jralls. It better utilizes for loops,
and usage of swap. We also try to make sure the null guid is not freed since it's
reused, and catch a c++ exception to make sure it doens't escape into C code when
parsing a GUID.

src/libqof/qof/guid.cpp

@@ -85,6 +85,15 @@ gnc_value_get_guid (const GValue *value)
     return val;
 }
 
+static GncGUID * nullguid {reinterpret_cast<GncGUID*> (new boost::uuids::uuid{0})};
+
+/*It looks like we are expected to provide the same pointer every time from this function*/
+const GncGUID *
+guid_null (void)
+{
+    return nullguid;
+}
+
 /* Memory management routines ***************************************/
 
 GncGUID *
@@ -99,7 +108,11 @@ guid_free (GncGUID *guid)
 {
     if (!guid)
         return;
+    if (guid == nullguid)
+        /*!!Don't delete that!!*/
+        return;
     delete reinterpret_cast<boost::uuids::uuid*> (guid);
+    guid = nullptr;
 }
 
 
@@ -111,23 +124,15 @@ guid_copy (const GncGUID *guid)
     return reinterpret_cast<GncGUID*> (ret);
 }
 
-static GncGUID * nullguid {reinterpret_cast<GncGUID*> (new boost::uuids::uuid{0})};
-
-/*It looks like we are expected to provide the same pointer every time from this function*/
-const GncGUID *
-guid_null (void)
-{
-    return nullguid;
-}
-
 /*Takes an allocated guid pointer and constructs it in place*/
 void
 guid_replace (GncGUID *guid)
 {
     static boost::uuids::random_generator gen;
     boost::uuids::uuid * val {reinterpret_cast<boost::uuids::uuid*> (guid)};
-    val->boost::uuids::uuid::~uuid();
-    new (val) boost::uuids::uuid (gen ());
+    val->boost::uuids::uuid::~uuid ();
+    boost::uuids::uuid temp (gen ());
+    val->swap (temp);
 }
 
 GncGUID *
@@ -169,25 +174,13 @@ guid_to_string_buff (const GncGUID * guid, gchar *str)
 {
     if (!str || !guid) return NULL;
 
-    static boost::uuids::string_generator str_gen;
-    stringstream ostr;
-    boost::uuids::uuid const & tempg = *reinterpret_cast<boost::uuids::uuid const *>(guid);
-    ostr << tempg;
-    string const & val (ostr.str());
-    /*unsigned size {val.size()};
-     size must equal GUID_ENCODING_LENGTH*/
-    unsigned stringspot{0};
-    for (unsigned destspot{0}; destspot < GUID_ENCODING_LENGTH; ++destspot, ++stringspot){
-        switch (stringspot){
-            /*there are hyphens in boost's output, and we need to skip them in our output*/
-            case 8:
-            case 13:
-            case 18:
-            case 23:
-                ++stringspot;
-        }
-        str[destspot] = val[stringspot];
-    }
+    boost::uuids::uuid const & tempg = *reinterpret_cast<boost::uuids::uuid const *> (guid);
+    unsigned destspot {0};
+    string const & val {to_string (tempg)};
+    for (auto val_char : val)
+        if (val_char != '-')
+            str [destspot++] = val_char;
+
     str[GUID_ENCODING_LENGTH] = '\0';
     return &str[GUID_ENCODING_LENGTH];
 }
@@ -195,9 +188,19 @@ guid_to_string_buff (const GncGUID * guid, gchar *str)
 gboolean
 string_to_guid (const char * str, GncGUID * guid)
 {
-    static boost::uuids::string_generator strgen;
-    boost::uuids::uuid * converted {reinterpret_cast<boost::uuids::uuid*> (guid)};
-    new (converted) boost::uuids::uuid (strgen (str));
+    if (!guid || !str)
+        return false;
+
+    try 
+    {
+        static boost::uuids::string_generator strgen;
+        boost::uuids::uuid * converted {reinterpret_cast<boost::uuids::uuid*> (guid)};
+        new (converted) boost::uuids::uuid (strgen (str));
+    }
+    catch (...)
+    {
+        return false;
+    }
     return true;
 }
 
@@ -236,11 +239,10 @@ guid_hash_to_guint (gconstpointer ptr)
 
     guint hash {0};
     unsigned retspot {0};
-    boost::uuids::uuid::const_iterator guidspot {guid->begin ()};
-    while (guidspot != guid->end ()){
+    for (auto guidspot : *guid)
+    {
         hash <<= 4;
-        hash |= *guidspot;
-        ++guidspot;
+        hash |= guidspot;
     }
     return hash;
 }

src/libqof/qof/guid.h

@@ -151,8 +151,8 @@ gchar * guid_to_string_buff (const GncGUID * guid, /*@ out @*/ gchar *buff);
  * This function accepts both uppor and lower case hex digits. If
  * letters outside the range of [a-fA-F] are passed, they are silently
  * replaced. If non-alphanumeric digits are given, this function will
- either return false or replace those values with others.
-. */
+ * either return false or replace those values with others.
+ */
 gboolean string_to_guid(const gchar * string, /*@ out @*/ GncGUID * guid);